Hybrid Double Perovskites Research Articles

Designing Double Perovskites with Organic Dications for Enhancing Stability and Photoelectrical Performance.

Recently, the research on developing lead-free double-B-cation halide perovskites has attracted attention. However, Cs2InBiCl6, the most promising one, was shown to be thermodynamically unstable. To improve the stability, organic dication DiMA2+ (i. e., (CH2NH3)+(CH2)3(CH2NH3)+) is introduced to design the new double perovskite DiMAInBiX6 (X=Cl, Br, and I) based on Cs2InBiX6 by replacing two Cs+ with a DiMA2+. Density functional theory calculations were performed to study the geometric and photoelectric properties of the newly designed materials. Unlike Cs2InBiX6, both DiMAInBiCl6 and DiMAInBiBr6 can exist stably against decompositions, indicating that the replacement of Cs+ by DiMA2+ will improve stability of double perovskites due to the staple effect. In addition, the replacement causes an increase in the band gaps of DiMAInBiX6. Particularly, the calculated band gap of DiMAInBiBr6 (1.31 eV) is close to the optimal value of single junction perovskite solar cell (PSC). Under ideal conditions, the PSC model constructed with DiMAInBiBr6 performs the best in theoretical simulation. This work proposes DiMAInBiBr6 as a promising light absorber of PSC, which has high stability and photoelectric performance. It also suggests that the replacement of Cs+ by DiMA2+ may serve as a rational and practical way to design new organic-inorganic hybrid double perovskites.

Radiation-Sensitive Layered Hybrid Double Perovskites Driven by a Dual-Ion-Woven Supramolecular Framework for X-Ray Tomography.

A promising candidate for X-ray detection is layered hybrid double perovskites (LHDPs) with excellent structural stability, but their sensitivity is generally limited by unsatisfactory interlayer charge transport. Herein, employing one ethylenediamine (EDA) chain as a structural inducer, we successfully obtain unusual Dion-Jacobson (DJ) phase LHDPs, (EDABr)4AgBiBr8 and (EDABr)4CuBiBr8, featuring a Ruddlesden-Popper-like (RP-like) interlayer. Thanks to the bridging of bromine anions, organic cations are linked via charge-assisted hydrogen bonds, where two ionic spacers are orderly woven into a supramolecular framework. Consequently, the RP-like interlayer space is regulated by the dual-ion-woven supramolecular framework with embedded charge-assisted hydrogen bond networks, remarkably enriching interlayer interactions and boosting charge transport. Through theoretical calculations, structural roles of the supramolecular framework are elucidated by extra orbital contribution and large diffusion barrier of Br anions. As proof of concept, the sensitivity of RP-like devices up to 5250 μC Gyair -1 cm-2 is a record-high of LHDP-based X-ray detectors for now, while a low detection limit (91 nGyair s-1) and outstanding radiation-resistant capability (50 Gyair) are achieved. Moreover, an oriented membrane device is prepared to demonstrate high-performance X-ray tomography. These findings offer a brand-new interlayer-modulation strategy for the construction of sensitive and stable scintillation semiconductors.

Radiation‐Sensitive Layered Hybrid Double Perovskites Driven by a Dual‐Ion‐Woven Supramolecular Framework for X‐Ray Tomography

AbstractA promising candidate for X‐ray detection is layered hybrid double perovskites (LHDPs) with excellent structural stability, but their sensitivity is generally limited by unsatisfactory interlayer charge transport. Herein, employing one ethylenediamine (EDA) chain as a structural inducer, we successfully obtain unusual Dion‐Jacobson (DJ) phase LHDPs, (EDABr)4AgBiBr8 and (EDABr)4CuBiBr8, featuring a Ruddlesden‐Popper‐like (RP‐like) interlayer. Thanks to the bridging of bromine anions, organic cations are linked via charge‐assisted hydrogen bonds, where two ionic spacers are orderly woven into a supramolecular framework. Consequently, the RP‐like interlayer space is regulated by the dual‐ion‐woven supramolecular framework with embedded charge‐assisted hydrogen bond networks, remarkably enriching interlayer interactions and boosting charge transport. Through theoretical calculations, structural roles of the supramolecular framework are elucidated by extra orbital contribution and large diffusion barrier of Br anions. As proof of concept, the sensitivity of RP‐like devices up to 5250 μC Gyair−1 cm−2 is a record‐high of LHDP‐based X‐ray detectors for now, while a low detection limit (91 nGyair s−1) and outstanding radiation‐resistant capability (50 Gyair) are achieved. Moreover, an oriented membrane device is prepared to demonstrate high‐performance X‐ray tomography. These findings offer a brand‐new interlayer‐modulation strategy for the construction of sensitive and stable scintillation semiconductors.

Impact of halogens modifications on physical characteristics of lead-free hybrid double perovskites compounds Cs2YCuX6 (X=Cl, Br, and I) for energy storage applications: First principles investigations

The purpose of this study is to examine the structural, electronic, optical, and thermoelectric features of novel double perovskite Cs2YCuX6 (X=Cl, Br, and I) for the first time in order to look for potential applications in solar power systems. Using first-principles calculations based on the widely recognized Density Functional Theory (DFT) and the PBE-Generalized Gradient Approximation (GGA) functional included in the WEIN2k package, the characteristics of the perovskites were determined. From the results of band structure and Total Density of States (TDOS) the energy band gap of Cs2YCuCl6, Cs2YCuBr6, and Cs2YCuI6 are observed 2.34 eV, 2.03 eV and 1.68 eV respectively. The PDOS outcomes shows that the formation of the valance and conduction bands is due to the hybridization of Cu-3d and halogen ions such that (X=Cl, Br, and I). The calculated values of goldsmith’s tolerance factor and formation energy reveal that the examined halide perovskites are structurally and thermodynamically stable. The electron localization function ELF and bader charge analysis show that the ionic nature between Cs and halogen ions X. Regarding the optical behavior, Cs2YCuI6has shown maximum absorption of electromagnetic radiation and conductivity in the ultraviolet and visible region i.e. (128–471 nm) which makes it a suitable candidate for optoelectronic and solar cell applications. The thermoelectric properties of the studied compounds have been calculated by means of the Boltztrap code. The presented findings unveil that amongst all studied compoundsCs2YCuI6 is best candidate for solar cell and thermoelectric applications due to higher conductivity, larger absorption range, significant Seebeck coefficient and higher Power factor.

Molecular Engineering Regulation Achieving Out‐of‐Plane Polarization in Rare‐Earth Hybrid Double Perovskites for Ferroelectrics and Circularly Polarized Luminescence

AbstractOut‐of‐plane polarization is a highly desired property of two‐dimensional (2D) ferroelectrics for application in vertical sandwich‐type photoferroelectric devices, especially in ultrathin ferroelectronic devices. Nevertheless, despite great advances that have been made in recent years, out‐of‐plane polarization remains unrealized in the 2D hybrid double perovskite ferroelectric family. Here, from our previous work 2D hybrid double perovskite HQERN ((S3HQ)4EuRb(NO3)8, S3HQ=S‐3‐hydroxylquinuclidinium), we designed a molecular strategy of F‐substitution on organic component to successfully obtain FQERN ((S3FQ)4EuRb(NO3)8, S3FQ=S‐3‐fluoroquinuclidinium) showing circularly polarized luminescence (CPL) response. Remarkably, compared to the monopolar axis ferroelectric HQERN, FQERN not only shows multiferroicity with the coexistence of multipolar axis ferroelectricity and ferroelasticity but also realizes out‐of‐plane ferroelectric polarization and a dramatic enhancement of Curie temperature of 94 K. This is mainly due to the introduction of F‐substituted organic cations, which leads to a change in orientation and a reduction in crystal lattice void occupancy. Our study demonstrates that F‐substitution is an efficient strategy to realize and optimize ferroelectric functional characteristics, giving more possibility of 2D ferroelectric materials for applications in micro‐nano optoelectronic devices.

Molecular Engineering Regulation Achieving Out-of-Plane Polarization in Rare-Earth Hybrid Double Perovskites for Ferroelectrics and Circularly Polarized Luminescence.

Out-of-plane polarization is a highly desired property of two-dimensional (2D) ferroelectrics for application in vertical sandwich-type photoferroelectric devices, especially in ultrathin ferroelectronic devices. Nevertheless, despite great advances that have been made in recent years, out-of-plane polarization remains unrealized in the 2D hybrid double perovskite ferroelectric family. Here, from our previous work 2D hybrid double perovskite HQERN ((S3HQ)4EuRb(NO3)8, S3HQ=S-3-hydroxylquinuclidinium), we designed a molecular strategy of F-substitution on organic component to successfully obtain FQERN ((S3FQ)4EuRb(NO3)8, S3FQ=S-3-fluoroquinuclidinium) showing circularly polarized luminescence (CPL) response. Remarkably, compared to the monopolar axis ferroelectric HQERN, FQERN not only shows multiferroicity with the coexistence of multipolar axis ferroelectricity and ferroelasticity but also realizes out-of-plane ferroelectric polarization and a dramatic enhancement of Curie temperature of 94 K. This is mainly due to the introduction of F-substituted organic cations, which leads to a change in orientation and a reduction in crystal lattice void occupancy. Our study demonstrates that F-substitution is an efficient strategy to realize and optimize ferroelectric functional characteristics, giving more possibility of 2D ferroelectric materials for applications in micro-nano optoelectronic devices.

Multi-dimensional lead-free hybrid double perovskite toward efficient and stable photocatalytic selective oxidation of toluene

With unique photoelectronic properties, perovskites have drawn attention in photocatalysis. However, their activity and stability especially in moist environments is not appealing, despite it was demonstrated that the construction of three-dimensional (3D) and low-dimensional counterparts could result in boosting of activity and stability, respectively. Here, a lead-free hybrid double perovskite ((DETA)BiBr6/Cs2AgBiBr6, DCABB) was fabricated by uniformly dispersing 0D DETABiBr6 (DETA3+ = NH3+(CH2)2NH2+(CH2)2NH3+) in the matrix of 3D Cs2AgBiBr6. Benefited from the passivation of Br defects and resistance of water by DETA3+, the stability of DCABB improved in comparison to pristine 3D Cs2AgBiBr6. Moreover, the formation of DCABB increased the adsorption of O2 and the accumulation of photogenerated electrons on the surface of catalyst, consequently boosting the generation of active O2− and OH species. The DCABB displayed higher photocatalytic performance than its components in toluene selective oxidation under visible light illumination, achieving a toluene conversion of up to 100 %.

Rare Earth Nitrate Hybrid Double Perovskites [Me4N]2[MLn(NO3)6] (M = Na-Cs; Ln = La-Gd, ex. Pm).

An exploration of the synthetic and structural phase space of rare earth hybrid double perovskites A2B'BX6 (A = organocation, B' = M+, B = M3+, X = molecular bridging anion) that include X = NO3- and B' = alkali metal is reported, complementing earlier studies of the [Me4N]2[KB(NO3)6] (B = Am, Cm, La-Nd, Sm-Lu, Y) (Me4N = (CH3)4N+) compounds. In the present efforts, the synthetic phase space of these systems is explored by varying the identity of the alkali metal ion at the B'-site. Herein, we report three new series of the form [Me4N]2[B'B(NO3)6] (B = La-Nd, Sm-Gd; B' = Na, Rb, Cs). The early members of the Na-series crystallize in the trigonal space group R3̅ from La to Nd where a phase transition occurs in the phase between 273 and 300 K, going from R3̅ to the high-symmetry, cubic space group Fm3̅m. The preceding trigonal members of the Na-series also undergo phase transitions to cubic symmetry at temperatures above 300 K, establishing a decreasing trend in the phase-transition temperature. The remainder of the Na-series, as well as the Rb- and Cs-series, all crystallize in Fm3̅m at 300 K. The temperature-dependent phase behavior of the synthesized phases is studied via variable-temperature spectroscopic methods and high-resolution powder X-ray diffractometry. All phases were characterized via single-crystal and powder X-ray diffraction and Fourier transform infrared (FT-IR) and Raman spectroscopic methods. These results demonstrate the versatility of the perovskite structure type to include rare earth ions, nitrate ions, and a suite of alkali metal ions and serve as a foundation for the design of functional rare earth hybrid double perovskite materials such as those possessing useful multiferroic, optical, and magnetic properties.

Computational analysis of hybrid double perovskite materials and their potential in photovoltaic and thermoelectric applications

Hybrid double perovskites are promising for use in next-generation solar cells. The priority is to address their critical problems and gain insight into their operation. The density functional theory is employed to obtain the mechanical, electronic, and optical properties of organic–inorganic double perovskites based on aluminum and gallium. The results revealed that the double perovskite materials are stable, as confirmed by calculating the formation energy and the elastic constant. Moreover, when using the TB-mBJ functional, the electronic properties obtained indicate that the direct band gap values are 1.39 eV and 2.72 eV for (NH4)2AgGaBr6 and (NH4)2AgAlBr6, respectively. Additionally, because of the direct band nature of (NH4)2Ag(Al/Ga)Br6, they exhibit excellent optical properties, including a high order absorption coefficient of 105 cm−1 and low reflectivity, making them useful for multiple optoelectronic applications outside of photovoltaics. Calculations of SLME revealed that (NH4)2AgGaBr6 and (NH4)2AgAlBr6 achieve single-layer efficiency of 32.87% and 8.36% respectively, emphasizing their viability for future applications. The results of the thermoelectric analysis suggest that these compounds have a promising potential for use in transport applications, as they demonstrate a higher figure of merit (ZT) compared to other compounds. Specifically, (NH4)2AgAlBr6 has a ZT value of 0.734, while (NH4)2AgGaBr6 has a ZT value of 0.737.

Prominent reverse saturable absorption of lead-free two-dimensional organic-inorganic hybrid double perovskites promoted by defects

Two-dimensional (2D) organic-inorganic hybrid perovskites have exhibited prominent reverse saturable absorption (RSA), yet their practical application is hindered by the lack of a defect-tolerance performance-enhancing strategy and lead-related toxicity. This study demonstrates that the realization of RSA via excited-state absorption is an effective strategy to achieve defect-promoted RSA in a series of lead-free 2D hybrid double perovskites (A4AgBiBr8), where A represents propylammonium (PA), butylammonium (BA), and hexylammonium (HA). Among these, the (PA)4AgBiBr8 shows the best performance. The nonlinear absorption coefficient of the solution-phase deposited thin film is as high as (2.0 ± 0.3) × 104 cm GW−1, a value that is competitive with those of most mechanically-exfoliated 2D hybrid lead halide perovskites and inorganic monolayer/few-layer 2D materials. Spectral characterization and density functional theory calculation demonstrate that Br vacancies in A4AgBiBr8 introduce abundant defect states, which act as intermediate states and enable efficient excited-state absorption. Consequently, a larger number of defect states results in a stronger RSA response.

Hybrid Double Perovskite Derived Halides Based on Bi and Alkali Metals (K, Rb): Diverse Structures, Tunable Optical Properties and Second Harmonic Generation Responses.

Double perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi-based double perovskite derived halides with the general formula of A2 BBiX6 (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp3 oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non-centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non-centrosymmetric materials, showing different particle-size-dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking.

Hybrid Double Perovskite Derived Halides Based on Bi and Alkali Metals (K, Rb): Diverse Structures, Tunable Optical Properties and Second Harmonic Generation Responses

AbstractDouble perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi‐based double perovskite derived halides with the general formula of A2BBiX6 (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp3 oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non‐centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non‐centrosymmetric materials, showing different particle‐size‐dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking.

Lead-free hybrid two-dimensional double perovskite with switchable dielectric phase transition

Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses, lightweight, and mechanical flexibility. Two-dimensional (2D) hybrid perovskites have demonstrated excellent promise for assembling dielectric switches, in which the dynamic motions of organic moieties afford driving force to trigger switchable dielectric phase transition. Here, we successfully assembled a new lead-free hybrid double perovskite, (CHA)4CuBiBr8 (1, CHA = cyclohexylammonium), adopting a typical 2D structural motif, which shows dielectric anisotropy and bistable behaviors during the reversible phase transition near Tc = 378 K (the Curie temperature). That is, its dielectric constants could be switched and tuned between high-dielectric and low-dielectric states. Structure analyses reveal that the ordered-disordered transformation of the organic CHA+ moiety and distortion of inorganic framework account for its phase transition. This result will stimulate further exploration of molecular dielectric switches in this 2D environmentally friendly family.

Lead-Free Double Perovskite Semiconductor with Rigid Spacer-Induced High-Tc Dielectric Switch Features.

Layered hybrid perovskites possess exceptional semiconductor features and structural versality, making them viable candidates for developing multifunctional dielectric phase-transition materials (PTMS). However, most PTMs based on layered hybrid perovskites still suffer from Pb toxicity and low operating temperature. The recently developed hybrid double perovskites provide a new routine to designed PTMs with desired working performance and environment-friendly chemical compositions. Herein, using rigid aromatic cations as templates, we have successfully synthesized a novel double perovskite (benzylammonium)4 AgBiBr8 (1), which consists of corner-sharing AgBr6 and BiBr6 layers and benzylammonium cations. Notably, 1 exhibits a high-temperature first-order reversible solid-state phase transition at 383/387 K (cooling/heating) and switchable dielectric performance around the temperature. Compared with the soft organic chain version of the compound, the phase transition temperature of 1 shows a large enhancement of 99 K, validating the correctness of the designing strategy. In addition, 1 also exhibits semiconductor characteristics with a calculated bandgap of 2.34 eV and an optical bandgap of 2.29 eV. Remarkably, the single crystal photodetector of 1 shows a low dark current (2.12×10-13 A), a high on/off ratio (1.77×103 ), and a fast response (τrise =125 μs and τdecay =419 μs). Such a lead-free phase transition material combined with semiconductor properties provides a new strategy to develop environmentally friendly multifunctional materials.

Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-ray Detection.

2D Dion-Jacobson (DJ) phase hybrid perovskites have shown great promise in the photoelectronic field owing to their outstanding optoelectronic performance and superior structural rigidity. However, DJ phase lead-free double perovskites are still a virgin land with direct X-ray detection. Herein,wehave designed and synthesized a new DJ phase lead-free layered double perovskite of (HIS)2 AgSbBr8 (1, HIS2+ = histammonium). Centimeter-sized (18 × 10 × 5 mm3 ) single crystals of 1 are successfully grown via the temperature cooling technique, exhibiting remarkable semiconductive characteristics such as a high resistivity (2.2 × 1011 Ω cm), a low trap state density (3.56 × 1010 cm-3 ), and a large mobility-lifetime product (1.72 × 10-3 cm2 V-1 ). Strikingly, its single-crystal-based X-ray detector shows a high sensitivity of 223 µC Gy-1 air cm-2 under 33.3V mm-1 , a low detection limit (84.2 nGyair s-1 ) and superior anti-fatigue. As far asweknow,wefirstly demonstrates the potential of 2D DJ phase lead-free hybrid double perovskite in X-ray detection, showing excellent photoelectric response and operational stability. This work will pave a promising pathway to the innovative application of hybrid perovskites for eco-friendly and efficient X-ray detection.

Discovering New Type of Lead‐Free Cluster‐Based Hybrid Double Perovskite Derivatives with Chiral Optical Activities and Low X‐Ray Detection Limit

Abstract2D chiral hybrid perovskites have recently emerged as outstanding semiconductor materials. However, most of the reported 2D chiral perovskites have limited structural types and contain high levels of toxic lead, which severely hinders their further applications. Herein, by using a mixed‐cation strategy, an unprecedented type of lead‐free cluster‐based 2D chiral hybrid double perovskite derivatives are successfully obtained, [(R/S‐PPA)4(IPA)6Ag2Bi4I24]·2H2O (1‐R and 1‐S), and [(R/S‐PPA)4(n‐BA)6Ag2Bi4I24]·2H2O (2‐R and 2‐S) (R/S‐PPA=R/S–1‐phenylpropylamine; IPA=isopentylamine; n‐BA=n‐butylamine). Their inorganic skeletons are linked by binuclear {Bi2I10} and infinite chain {Ag2Bi2I14}∞, in which bismuth clusters and multiple coordination modes (e.g., tetrahedral AgI4 and octahedral AgI6) are introduced into the double perovskite system for the first time. This introduction induces distortion of the inorganic layer, which may facilitate the transfer of chirality from the chiral cations into achiral double perovskite skeletons. Further, circular dichroism measurements and circularly polarized light detection confirm their inherent chiral optical activities. In addition, 1‐S exhibits an ultralow X‐ray detection limit of 129.5 nGy s−1, which is 42‐fold lower than that of demands in regular medical diagnosis (5.5 µGy s−1). This study provides a pathway to construct novel type of lead‐free cluster‐based double perovskite derivatives.

Elucidating the Mn2+ Dopant Sites in Two-Dimensional Na–In Halide Perovskite

The layered hybrid double perovskites (LDPs) possess excellent stability and environmental friendliness, which makes them remarkable semiconducting materials. Contrary to significant advancements, the nonfluorescent nature at ambient temperature and pressure is still a major hurdle in this intriguing family. Here, we demonstrate doping of the transition metal cation Mn2+ in two-dimensional (2D) (PEA)4NaInCl8 (PEA = phenylethylamine) LDP, by a solution-processed crystallization method. This results in broadband emission at ambient conditions and initial contraction followed by expansion of host lattice on increasing dopant concentration. A higher dopant feed ratio in this wide band gap material leads to the absorption at 2.95 eV due to the 6A1 (6S) → 4A1 (4G) transitions on Mn2+ centers. First-principles calculations based on density functional theory (DFT) confirm that Mn2+ in substitutional sites results in lattice contraction while interstitial site Mn2+ doping leads to lattice expansion. The potential of Mn2+ to improve optical and magnetic properties of host lattice and a deeper understanding of distribution of Mn2+dopant make these LDPs a promising material for emitters for solid-state lighting and magneto-optical applications.

Water-driven Successive Structural Transformation in a Two-Dimensional (2D) Lead-Free Hybrid Double Perovskite.

Hybrid organic-inorganic halide perovskites (HOIPs) have received continued interest for their structure diversity and potential application in optoelectronic, solar cells, nonlinear optics (NLO), and ferroelectrics. Structural symmetry breaking induced by water molecules in single-crystal-to-single-crystal (SCSC) transformations is beneficial to develop ferroelectrics or second-harmonic generation (SHG) materials. Along this line, a water-containing two-dimensional (2D) double perovskite, (C6H16N2)2AgBiBr8·H2O (1), was prepared. Acentric 1 suffered a twice SCSC transformation when subjected to dehydration and rehydration, where the new centric (C6H16N2)2AgBiBr8 (2) and acentric (C6H16N2)2AgBiBr8·0.5H2O (3) were generated. In contrast to the irreversible transformation from 1 to 2 (symmetry: P21 → Pmna), it is prominent that the reversible conversion of centric 2 to acentric 3 (symmetry: Pmna ↔ P21212). The result validated the effect of guest water on inducing structural transformation and symmetry breaking of 2D perovskites, inspiring further explorations on water-involved 2D materials.

Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry.

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A2B'BX6 with the formula ((CH3)4N)2KLn(NO3)6 (Ln = La-Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, Fm3̅m. This series was obtained via evaporative crystallization from a mixture of Ln(NO3)3, KNO3, and (CH3)4N·NO3 in a 1:1:2 ratio from either H2O or 4.0 M HNO3. In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N═O oxygen atoms coordinating the potassium on the B' site in an octahedral six-coordinate environment. The two remaining charge-compensating (CH3)4N+ cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. This series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.

Synthesis, dielectric, magnetic, and photoluminescence properties of two new hybrid rare-earth double perovskites

Two new organic–inorganic hybrid double perovskites (R3HQ)4CsSm(NO3)8 (1) (R3HQ = (R)-(-)-3-quinuclidinol) and (R3HQ)4CsEu(NO3)8 (2) were synthesized and characterized. Compounds 1 and 2 exhibit obvious phase transitions at 379 and 375 K, respectively, confirmed by differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction. The rapid switching between high- and low-dielectric states makes it a typical dielectric material with a switchable dielectric constant for thermal stimulus response. Furthermore, 1 and 2 show attractive photoluminescence and paramagnetic behavior, and the fluorescence quantum yield of 2 reached 14.6%. These results show that compounds 1 and 2 can be used as excellent candidates for multifunctional intelligent materials, which also provides a new way for development of multifunctional materials.